Electrical gun hammer and nail driver

ABSTRACT

An electrically operated hammer and nail driver in which nails are fed from a magazine and are aligned and driven forward by hammer means through a discharge nozzle, and includes a solenoid having reversely wound double coils and an axially reciprocable armature within the solenoid, and a reversing switch in the path of the hammer means and adapted to supply current to the double coils of the solenoid to effect reciprocation of the hammer means.

United States Patent 72] Angel Moreno,

4266 Old Orchard Ave., Apt. No. 23, Montreal 28. Quebec. Canada 805,291

Mar. 7, 1969 Jan. 5, 1971 Inventor App]. No. Filed Patented ELECTRICAL GUN HAMMER AND NAIL DRIVER 7 Claims, 15 Drawing Figs.

US. Cl

227/121, 227/ l 31 B25c 5/06 227/121, 131

Int. Cl Field of Search References Cited UNITED STATES PATENTS 10/1926 Davis et al. 2,033,018 3/1936 Weber 2,572,012 10/1951 Curtis Primary Examiner-Granville Y. Custer, Jr. Attorney-Jerry B. Cesak f as 35,14 74 134 m6 PATENTED JAN 5197! 35521627 SHEET 1 BF 4 m2 ggy: I FIG. /5

INVENTOR 2/4 2/2 MORENO A TTORNE YS ATENTED JAN 5 1971 saw 2 or 4 INVENTOR A. MORENO PATENTED JAN 5 sum u or 4 I N VE N TUR A. MORENO A T'I'OR NI'I YS ELECTRICAL GUN HAMMER AND NAIL DRIVER The present invention relates to an electric hammer, and

particularly relates to a semiautomatic electric hammer gun capable of driving nails of varying size and length.

Electric hammers for automatically or semiautomatically driving nails quickly and precisely are finding increased favour in view of increased labour costs. The use of an electric hammer greatly increases nailing speed resulting in increased production and saving in construction costs, and it is a main object of the present invention to provide an electric nail harnmering device which will quickly drive nails with precision and accuracy.

In general the hammer of the present invention consists of a solenoid having reversely wound double coils and an armature in the solenoid mechanically linked tothe hammer member, and a nail supply and nail driving mechanism contacted'by the hammer member for driving a nail, and a reversing switch for selectively controlling electric current-flowto one or other of the solenoid coils.

Electric hammers for driving nailsare known in the an. In all of the known devices the movement of the reciprocating armature member is transferred directly to anail being driven. This direct impact of the armature against a nail or against an assembly disposed between the armature and the nail is damaging both to the armature and to the solenoid coils resulting in the shortening of the useful life of the device. The present invention overcomes this disadvantage by mechanically linking the armature to a hammering member which effects the impact against the nail. This arrangement'removes the armature from direct impact hence lengthening the life of the device. The provision of the mechanical linkage and the hammering member in addition to saving the armature and coils from undue wear and damage also provides for increased mechanical advantage and an increased impact force not possible when the armature is used directly as a hammering member. f

In addition to providing a devicefor quickly and accurately driving nails the present invention provides a device having a nail supply or magazine to automatically feed nails to the nailing mechanism of the device for increased efficiency. The magazine will accommodate a supply of nails of varying size and length and permit continued operation of the device with nails of varying size without any change of the device being necessary.

It is a further object of the invention to provide an electric hammering device having a nail supply magazine which will automatically feed nails for nailin'g whether the nails in the magazine be of identical size or of varying size and length.

It is a further object of the present invention to provide an electrical hammering device having a reversely wound doublecoil solenoid and a common armature therein for controlling by mechanical lever linkage the reciprocal movement of a hammering member and to hammering member dampening means for absorbing impact on the reverse stroke of the hammering member. v

It is still a further object to provide anelectrically operated device for quickly and accuratelydriving nails comprising a casing and a reversely wound double-coil solenoid and an armature within the solenoid and means to alternate current flow to one or other of the coils, and a hammer member mounted for reciprocal movement connected'to one end of the armature by mechanical lever linkage, and a naildriving assembly mounted for reciprocal movement within the casing to contact and drive a nail under the influence of the hammer member, and a magazine for automatically and sequentially feeding nails to the nail driving assembly.

These and other objects of the invention will become apparent from the following disclosure in conjunction with the accompanying drawings wherein:

FIG. 1 is a side elevation of the electric hammer gun accord-- FIG. 3 is a top plan view partially in section of the hammer shown in FIG. 2; Y v I FIG. 4 is a top view partially in section of the forward portion of the gun shown in FIG. 3 and showing the hammering mechanism in a forward position in the act of hammering (sheet I);

FIG. 5 is a sectional view along line 5-5 of FIG. 2;

FIG. 6 is a sectional view along line 6-6 of FIG. 2;

FIG. 7 is a sectional view along line "7-7 of FIG. 2;

FIG. 8 is a sectional view along line of FIG. 2;

FIG. 9 is a sectional view along line 9-9 of FIG. 2 (sheet 3);

FIG. 10 is a sectional view along line 10-10 of FIG. 2 (sheet I FIG. 11 is a plan view 'of one nail passageway forming plate shown in FIGS. 3, 4, 8, 9 and 10 (sheet 1);

FIG. 12 is a-plan view of the other of the nail passageway forming plates shown in FIGS. 2, 3, 4, 8', 9 and I0 (sheet 1);

FIG. 13 is a side elevation'in' section of a, spring-loaded pneumatic electric contact switch shown in FIGS. 2 and 3; (sheet 2);

FIG. 14 is a front elevation ofthe switch shown in FIG. I3 taken along the line 14-14 of FIG. 13 (sheet 2'); and,

FIG. l5'is a diagrammatic representation of the electrical circuitry of the present invention (sheet 1 With particular reference to the drawings'the casing of the device'is shown at numeral 2. The device is'formed generallyin the shape of a hand gun having a handle section 4 and a barrel section 6. A double-coil solenoid indicated generally at 8 is secured beneath the barrel section and consists of two reve rsely wound coils wand 12 having a common armature l4.'The armature 14 is axially slidable within the coil windings in known manner and coil 10 is wound to produce, when energized, an electromagnetic field moving the armature 14 forward or to the left in FIG. 2, and coil winding 12 is wound to produce, when energized, an electromagnetic field moving armature rearwardly or to the right. Thus by alternating energization'of the coils l0 and 12 a reciprocal axial movement is imparted to armature I4.'The casing of thedevice is provided with a projection 16 to accommodate the forward movement of the forward end of thearm'ature l4, and the rear end I8 of the armature 14 is provided with laterally projecting pins 20 (see also FIG. 6), which are received within slots 22 provided in hammer lever 24. The lower end of the lever 24 is'pivotally mounted to the device casing by a pivot pin 26 (see also FIG. 6). The upper end of the lever 24 is provided with two rollers 28 which are positioned within a vertical slot 30 (see also FIG. 3) provided in a hammer member 32. This hammer 32 which is clearly shown in FIGS. 2, 3, S and 6, is provided with four ball bearing mounted rollers 34 having axes of rotation in a horizontal plane, and eight ball bearingrnounted rollers 36 having axes of rotation in a vertical plane; The interior of the .barrel of the casing is provided with two parallel longitudinal track members, an upper track 38 and a lower track 40 is clearly shown inthe drawings. The two top rollers 34 which are axially horizontal mounted ride against the lower surface of the upper track 38 and the two lower rollers 34 ride against the upper surface of the lower track 40L Two of the four upper rollers 36 which are axially vertical ride against each side of the upper track 38, with two of the lower rollers 36 riding against each side of the lower track '40. v

Thus it will be appreciated that the interaction of the ball bearing mounted rollers on the tracks 38 and 40 will maintain the manner 32 in alignment on the tracks and permit substantially friction-free reciprocal longitudinal movement of the hammer within the barrel. The extent of reciprocal movement similar reasoning applies to the other components of the device to be discussed in more detail below, with parts subject. to wear or strain being made of more durable material.

Also mounted in the barrel 6 and in front of the hammer 32 is a carriage 42 carrying a forwardly projecting nail driving rod 44. The carriage 42 is provided with four rollers 46 mounted with their axes vertical, the top two'of the rollers 46 riding on the sides of the upper rail 38 and the lower two of the rollers 46 riding against the sides of the lower rail 40 in the same manner as the hammer 32. The carriage is also reciprocally movable longitudinally within the barrel with the forward tip 47 (see FIGS. 3 and 4) of the rod 44 contacting the head of a nail (positioned by a nail supply assembly or nail magazine to be described in more detail below) to drive the nail, under the hammering action ofthe hammer 32.

The carriage 42 and the rod 44 is normally urged to a rearward or rest position shown in FIGS. 2 and 3 under the action of a coil tension spring 48 (see FIGS. 3, 4, 5, 6 and 7). One end of the spring 48 is secured to the casing of the device at 49 (see FIGS. 3 and and 6) and the other end is secured to a spur or flange 50 projecting from the side of the carriage 42. The action of the spring 48 urges the carriage 42 and rod 44 to the right as shown in FIGS. 3 and 4 or towards the handle end 4 of the barrel.

Movement of the hammer 32 to the left in FIGS. 2 and 3 moves the carriage 42 and nail diving rod 44 also to the left and against the action of spring 48 to drive a nail from the barrel and into the material to be nailed. After each hammering stroke the hammer retreats to the right ready for the next stroke as will be explained in more detail below, but the carriage is prevented from movement to the right after a nailing sequence has started by a saw tooth rack 52 carried by the easing and a rack contacting spring-loaded lever 54 assembly carried by the rod 44. The rack 52 is clearly shown in FIGS. 3 and 4. The lever 54 is pivotally mounted to the rod 44 at 56 and is spring loaded (by a spring not shown) to impart an outward movement to the end of the lever 54 which is provided as a rack contacting point 58. As hammering by the hammer 32 proceeds carriage 42 is moved to the left (in FIGS. 2 and 3) with the point 58 sequentially engaging the saw teeth of the rack (see FIG. 4) to prevent return of the carriage 42 to the right under the tension of spring 48 when the force of the hammer 32 is removed. This maintains the forward end 47 of the rod 44 in contact with the head of the nail 59 being driven. When the hammer 32 has moved the carriage 42 and rod 44 to the forward position as when the nail is driven fully into the material, the beveled front face 60 of the lever 54 contacts the beveled projection 62 of the rack '52 pivoting the lever 54 toward the rod 44.

The rod also carries a lever retaining mechanism generally indicated by numeral 64. This mechanism .consists of a springloaded catch 66 which is pivotally mounted at 68. The catch 66 is maintained in the position shown infull lines in FIG. 3 by the action of spring 70. As explained as the carriage 42 and rod 44 are moved to the extreme forward position the beveled face 60 on the lever 54 contacts the beveled projection 62 to pivot the end of the lever against the catch 66. The cam action of the beveled face 72 on the lever against the beveled face 74 on the catch 66 displaces the catch against the action of spring 70. As the lever continues to pivot under the cam action of beveled face 60, the faces 72 and 74 slide over and off each other allowing spring 70 to return the catch 66 to the position shown in both full and broken lines in FIG. 3 to hold the lever in a retained position as shown in dotted lines in FIG. 3 with the lever point 58 clear of the teeth on rack 52. The spring 48 is then able to return the carriage 42 and rod 44 rearwardly or to the right as the hammer moves rearwardly.

As the lever 54 moves to the right past the rack 52, a cam surface 78 provided on the lever contacts'a cam surface 80 carried by the gun casing to urge the lever 54 from behind the retaining catch 66 (by the cam action of beveled surface 60 on catch beveled surface 82)'to assume the rack contacting position shown in full lines in FIGS; 3 and ready for another nail driving operation. 1

Maximum outward movement of the lever 54 is controlled by a retaining bar 84 carried by the rod 44.

The nails to be driven by the gun hammer device are carried by a nail supply assembly or magazine shown generally at 86. The supply assembly consists of a container 88 secured to the gun casing, having a nail filling door 90 pivotally mounted at 92 and with locking means 94.

The nail supply container is provided with a partition 96 having a central aperture 98 running substantially the full length thereof (see FIG. 2) to maintain the nail supply (shown generally at 100) in proper alignment. The nails are urged inwardly toward the gun barrel and nail aligning passageway by a compression spring 102 provided on one side of the partition 96 and a second compression spring 104 provided on the other side. These springs urge the most inward nail 105 against the outside surface of a first nail passageway plate 106 shown in side view in FIG. 11, and the approximate position where the most inward nail 105 will contact the plate 106 is shown in broken lines in FIG. 2. I

The inner end of the magazine 86 is provided with a series of spring-loaded prongs 107 (with springs 109) to assist in maintaining the nails within the magazine in proper alignment. The inner ends of the prongs are beveled facing the direction of nail movement to permit retraction (by cam action) of the prongs against the action of springs 109 during movement of the nail head.

A nailing rod passageway is formed between the first passageway plate 106, and a second passageway plate 108 spaced a distance from the first plate to permit passage therebetween of the nail driving rod 44. See FIGS. 3, 4, 7, 8, 9 and 10. The second nail passageway plate 108 is shown in side view in FIG. 12, with the elongate slot 110 being provided to permit forward travel of the lever 54 and lever retaining 64 mechanism carried by the rod 44 and discussed above.

The forward portion 111 of the plate. 108 provides a flat surface for the movement of a nail thereover, and a guide plate 112 is held in a slot 114 in plate 106 by springs 116 to maintain the nail in proper alignment against surface 111 of plate 108. See FIG. 3. The inner end of the spring-loaded plate 112 is curved as at 118 to guide the point of an advancing nail into slot 114 and into the nail passageway. See FIG. 4. The T-head slot 120 provided in plate 106 is of course to permit passage of a nail head from one side of the 'plate into the nailing passageway.

The side boundaries of the nail passageway are of course defined by plates 106, 108 and 112. The'proper vertical alignment of the nail in the passageway is provided by a number of guide plugs 122 positioned between the casing 2 and the plate 108. The inner ends 124 of the plugs are beveled facing the direction of nail travel and project into the nail passageway through apertures 126 (See FIG. 12) provided in the plate 108. The plugs 122 are supported by springs 128, and thc beveled faces of the inner ends 124 permit retraction of the plugs 122 from the passageway upon contact by the head of the nail as it moves along the passageway. The upper row of guide plugs are spaced from the lower row of plugs a distance approximately the thickness of the'shank of a nail to provide proper nail alignment.

A nail 59 positioned between the two plates 106 and 108 is driven by rod 44 carried by carriage 42. The carriage is also provided with a second rod 130 projecting forwardly and parallel with but spaced from the rod 44. The rod 44 moves on the inner side of the plate 106 with the rod 130 on the outer end as rod 44 is driving one nail 59 the-rod 130 contacts the head of the most inward nail carried by the nail magazine and urges same along the outer surface of plate 106 with the curve 118 on plate 116 guiding the point of the nail 105 into the slot 114 in plate 106. (See FIG. 4). This nail 105 cannot enter the nail passageway due to the presence of a portion of the nail 59 being driven and the driving rod-44, but it will be advanced and held in the slots 114 and in plate 106 by spring-mounted guide plate 112 and magazine'spring 104. After the driven nail 59 has been advanced out of the passageway and into the material being nailed and the driving rod has retreated from the nail passageway the springs 116 and 104 will urge nail 105 into the passageway ready for the next nailing operation.

The retraction of carriage 42 and rod 44 to the rearward or right position shown in FIG. 2 will also retract nail advancing rod 130 permitting the springs 102 and 104 in the nail magazine 86 to advance the next most inward nail against plate 106 ready for advancement of the rod 130 A nail having a flattened T-shaped head as shown in FIG. 2 is preferably used with the device of the invention for efficient trouble-free operation, although other nails available on the market may be used.

The structure shown in the attached drawings will drive nails of varying length from about to about 2 V2 but modification to permit the driving of longer or shorter nails is possible without departing from the scope of the invention.

Nails of all one size may be driven in sequence, or nails of varying size and length may be randomly placed in the magazine with equally efficient operation.

As described above a nail is driven by the reciprocal hammering movement of hammer 32 caused by alternating the current supply on the two solenoid coils and 12. The energization of coil 10 causes forward movement of the armature shaft 14 and the hammer 32 to strike against the surface 132 of the nail driving rod carriage 42 which in turn faces forces the nail along the barrel and into the material being nailed. After the forward motion of the hammer the current flow to solenoid coil 10 is stopped and electric current is supplied to solenoid coil 12 to cause armature 14 and hammer 32 to move rearwardly to the position shown in FIG. 2. Electric current is then resupplied to coil 10 to effect a forward hammering movement to hammer 32 and so on until the nail has been driven out of the gun barrel.

The reciprocal hammering movement of the hammer 32 is caused by alternating current supply to the coils 10 and 12. This alternating is effected by a current alternating or reversing switch 134 shown generally at in FIGS. 2 and 3 and more specifically in FIGS. 13 and 14. The switch 134 actually is a current alternating switch and dampening assembly consisting of a hollow cylindrical member 136 which is secured to a plate 138 fixed to the interior casing of the device at the rearmost end of the barrel of the gun hammer. The cylinder member 136 carries four rod members 140 which are slidably reciprocal therein. The forward end of the rods carry a plate 142 against which the rear surface 144 of the hammer 32 will strike during return movement of the hammer, and the rearward end of the rods carry a plate 146 to which is attached double contact points 148 and 150. Reciprocal movement of the plate carries the contact points 148 and 150 between two stationary contact points 152 and 154 respectively The rear stationary contact point 154 is wired to the solenoid coil 10 and the front stationary contact point 152 is wired to the sole noid coil 12. Electric current is supplied to the movable contact points 148 and 150 and it will be appreciated that the positioning of the movable contacts 148 and 150 will determine the current flow to the solenoid coils. The electrical circuitry of the device will be described in more detail later.

The stationary cylinder 136 is provided with a piston 156 (see FIG. 13) secured to a piston rod 158 which in turn is secured to rear plate 146. The end of the cylinder adjacent the plate 146 is provided with a wall 160, and the piston rod is longitudinally slidable through an aperture (not numbered) provided therein. The piston 156 and plates 142 and 146 will tend 10 be held in the position shown in FIG. 13 by the force exerted by tension spring 162 between the wall 160 and the piston 156. The wall 146 is provided with a series of apertures 164 as is clearly shown in FIG. 14 which is a sectional view taken generally along line 14-14 of FIG. 13. The piston 156 carries a circular disc assembly 166 which is also axially movable within the cylinder, and the wall of the cylinder is provided with a plurality of apertures or ports 168 encircling the cylinder. The ports 168 are closed by the disc assembly 166 when the switch is in the position shown in FIG. 13 but will open when the piston .156 is moved against the force of spring 162 due to the impact of hammer 32 against the plate 142. A band 170 having apertures 172 (see FIG. 3) therein corresponding to the ports 168 provided in the cylinder wall encircles the cylinder adjacent the ports, and-the band 170 is circumferentially adjustable by means of a worm set screw 174 to enable adjustment of the opening size of the ports 168 to control air flow therethrough. This adjustment may easily be made by providing the worm set screw 174 with a slotted head as shown.

In the position shown in FIG. 13 the current reversing and dampening switch 134 is shown in the forward position which the switch will assume during the forward hammering movement of the hammer 32 due to the force of spring 162. When the switch is fully extended as shown the hot" contact 148 will contact switch contact 152 to supply current to the return solenoid 12. This will cause the armature I4 and hammer 32 to move rearwardly with the rear surface 144 of the hammer 32 contacting plate 142 and carrying the piston 156 back against the force of spring 162. The solenoid 12 moves the hammer 32 rearwardly with considerable speed and the impact with plate 142 is dampened by both the action of the spring 162 and pneumatic dampening action caused by forcing the air within the cylinder out through apertures 164 due to the rearward displacement of the piston. The rearward movement of piston 156 and valving disc 166 opens ports 168 to permit air flow into the cylinder 136 through ports 168. Thus rearward movement of the hammer is dampened and stopped without damaging impact or any appreciable chuck or jerk of the device.

With the hammer in its full rearward position the switch is in the position shown in FIG. 2, with movable contact 150 in contact with stationary contact 154 permitting current flow to solenoid 10 which results in the hammer 32 moving quickly forwardly to meet carriage 42 .and hence drive the nail. Upon release of the pressure from the hammer 32 the spring 162 in the reversing switch will move the switch to the position shown in FIG. 13, but this movement will be pneumatically dampened by the air within the cylinder being forced through ports 168. The size of the ports 168 is adjustable as discussed above, and accordingly the rate of movement of the piston and movable contact is readily adjustable to achieve a time lapse between the time when the contacts 150 and 154 are broken and the time when the contacts 148 and 152 are made to ensure that the full forward momentum of the hammer is transferred to the carriage 42 prior to activation of the return sole noid 12.

The electrical circuitry of the apparatus will now be described with particular reference to FIGS. 1, 2, 3 and 13. Electric current is introduced into the device by wires 178 and 180 which may be fused as at 182 to prevent damage to the wiring in the event of a short circuit. The incoming wire 178 leads to a trigger switch 184 which when depressed effects a contactwith contact 186 on a safety switch 188. The switch 188 is rotatable by handle 190 (see FIG. I) and the apparatus is operable only when the handle is rotated to the ON position with contact 186 positioned directly behind the contact 192 on the trigger 184. The safety switch is provided to prevent accidental operation of the device.

The switch 188 is connected by a wire 194 to one contact of breaker points shown generally at 196. The contact 198 is normally maintained in contact with contact 200 of the breaker points 196 by conductive spring 202 but the contact at 196 will be broken by a nonconductive projection 204 on the hammer lever 24 when the hammer 32 has reached its furthest forward point of travel (see broken lines in FIG. 2) as when a nail is completely driven into the material being nailed. The opening of the breaker points at l96 will break the circuitry of the device and render the device inoperative. The contact 200 of the breaker points 196 is connected by wire 206 to the movable double-contact points 148 and 150 of the reversing switch 134. A wire 208 contacts the forward stationary contact point 152 with return solenoid 12, andwire 210 connects the rear contact point 154 with the drive or hammering solenoid l0, and return wiring 180 completes the double wire installation.

When the breaker points 196 are opened due to the forward furthermost movement of the hammer 32, the circuitry is broken and the movable components rendered stationary. The circuitry is closed again by depressing pushbutton switch 212 (with the trigger depressed) to permit current flow through wire 214 and wire 216 to stationary contact 152 to activate solenoid 12 to move armature and hammer lever 24 rearwardly to permit closure of the breaker points 196 and restoration of current flow to the movable double-contact points 148 and 150 of the alternating or reversing switch 134.

A light 218 (see also FIG. 1) may be positioned in the circuit in series with the double-contact points 148 and 150 to advise the operator that current is being supplied to the double-contact points and that the circuit is complete and ready for operation.

The above circuitry is shown in FIG. 2 as actually arranged in the device, and diagrammatically in FIG. 13 where like numerals indicate like parts.

The operation of the hammer gun will now be described.

A supply of nails of equal or varying length are placed in the nail magazine 86, the magazine springs 102 and 104 inserted and the door 90 closed and locked.

Safety switch handle 190 (see FIG. '1) is then rotated clockwise to the ON position to position switch contact 186 directly behind trigger contact 192. The muzzle end of the barrel is then placed against the material into which a nail is to be driven, and trigger 184 depressed to close contacts 192 and 186 to supply electrical current through wire 194, breaker points 196 and wire 206 to the movable double-contact points 148 and 150 carried by the reversing switch 134. With this circuit complete the light 218 will go on, and the device will begin a nail driving operation. If however depressing trigger 184 does not start the hammering procedure and the light does not go on, it means that the breaker points 196 are open and the hammer 32 is in the extreme forward position. The hammer 32 is returned to its rearmost position by momentarily depressing pushbutton switch 212 to supply current to return solenoid 12 thus allowing the points 196 to close. The return of the hammer 32 to the rear position will of course enable spring 48 to return carriage 42 and driving rod 44 and advancing rod 130 to their rearmost position and permit the springs in the magazine to urge the innermost nail into contact with the outer surface of nail passageway forming plate 106. See FIGS. 3 and 1].

Depression of trigger 184 will not permit current flow to the movable contact points 150 which is in contact with stationary contact 154 and hence to the winding of drive solenoid 10. The electromagnetic field producedby current flow through the winding of coil will urge armature 14 and hammer 32 forwardly with the hammer 32 striking carriage 42 and forcing same forwardly in the barrel.

As we have assumed that a fresh supply of nails has just been placed in the magazine, there will not be a nail in the passageway between plates 106 and 108, and this first forward movement of the carriage 42 will not eject a nail from the barrel but advancing rod 130 will advance a nail into the slot 114 in plate 106 and ready for positioning in the passageway by the spring 116 loaded guide plate 112 when the carriage and nail driving rod 44 are returned to their-most rearward position shown in FIG. 2.

The forward movement of hammer 32 and hammer lever 24 -will cause point 204 to break the contact at 196 thus stopping material being nailed. If the nail is of the shorter variety and the material into which it is being driven is reasonably soft, only one hammer stroke may be necessary to drive the nail completely into the material.

I If however a longer nail is being driven, two or more strokes of the hammer 32 may be required. After each forward hammer stroke the reversing switch 134 will switch current flow from solenoid coil 10 to solenoid coil 12 which will cause the hammer to assume its most rearward position where the switch 134 is again reversed to impart forward movement to the hammer. The reversing current flow selection at switch 134 and the reciprocal hammering movement of hammer 32 will continue until the carriage 42 has reached its most forward position with lever 24 breaking the points at 196 to cease operation. At this point retaining lever 54 will be locked clear of rack 52 and depression of switch 212 will return the hammer 32 and carriage 42 to a position ready to begin the next nailing sequence as shown in FIG. 2.

The retaining lever 54 in contact with rack 52 holds the carriage 42 and nail driving rod forward in contact with the driven nail during the reciprocal hammering movement of the hammer. This is clearly shown in FIG. 4.

Various modifications of the very specific embodiment discussed above are of course within the scope of the present invention as defined by the appended claims.

Iclaim:

1. An electric hammer assembly comprising a casing having a rear hand grip end and a forward nail discharge nozzle and a solenoid having reversely wound double coils mounted within the casing and an axially reciprocable armature within the solenoid, one end of the armature being pivotally attached to a lever, said lever having one end pivotally mounted within the casing and the other end connected to a hammer member mounted for forward and rearward reciprocable movement within the casing, and a reversing switch positioned rearwardly in the casing and in the path of travel of the hammer member to alternatively supply electric current to one of the coils of the solenoid to move the armature and hammer member in a forward direction and to supply current to the other of the coils to move the armature and hammer member in the rearward direction, and a carriage mounted for forward and rearward reciprocable movement positioned forwardly of and in the path of travel of the hammer, and a nail driving rod on the carriage projecting forwardly into a nail passageway, and a spring-loaded nail'supply magazine for sequentially supplying nails to the passageway, and trigger switch means for selectively supplying electric current to the reversing switch.

2. Assembly according to claim 1 wherein the alternating switch is spring loaded and is activated by contact with the hammer member to supply current, to. the solenoid coil to move the hammer forwardly andaway from the alternating switch, the spring acting to activate the alternating switch to supply current to the coil to move the hammer rearwardly and toward the switch when the switch is not being contacted by the hammer member.

3. Assembly according to claim 2 further comprising a set of breaker points positioned adjacent the lever, said points being opened by the lever when the hammer member reaches its forwardmost position to cause electric current flow to the alternating switch, and a pushbutton switch to supply electric current to the coil to move the hammer rearwardly and close the breaker points.

4. Assembly according to claim 1 further comprising a spring secured at one end to the casing and at the other end to the carriage and urging the carriage rearwardly, and a rack secured to the casing adjacent the nail driving rod and a springloaded lever carried by the rod engaging the rack to maintain the rod and carriage in a forward position during a nailing operation, said spring-loaded lever being disengaged from the rack when the rod and carriage reach their forwardmost position. v

5. Assembly according to claim 1 further comprising a forwardly projecting nail advancing 'rod carried by the carriage and parallel to the nail driving rod, said nail advancing rod advancing the nails in the nail supply magazine to maintain one nail in a position adjacent the nail passageway during the driving of a nail by the nail driving rod, and spring means urging the one nail into the nail passageway-upon rearward move ment of the carriage and the nail driving rod.

6. Assembly according to claim 1 further comprising an air 

1. An electric hammer aSsembly comprising a casing having a rear hand grip end and a forward nail discharge nozzle and a solenoid having reversely wound double coils mounted within the casing and an axially reciprocable armature within the solenoid, one end of the armature being pivotally attached to a lever, said lever having one end pivotally mounted within the casing and the other end connected to a hammer member mounted for forward and rearward reciprocable movement within the casing, and a reversing switch positioned rearwardly in the casing and in the path of travel of the hammer member to alternatively supply electric current to one of the coils of the solenoid to move the armature and hammer member in a forward direction and to supply current to the other of the coils to move the armature and hammer member in the rearward direction, and a carriage mounted for forward and rearward reciprocable movement positioned forwardly of and in the path of travel of the hammer, and a nail driving rod on the carriage projecting forwardly into a nail passageway, and a spring-loaded nail supply magazine for sequentially supplying nails to the passageway, and trigger switch means for selectively supplying electric current to the reversing switch.
 2. Assembly according to claim 1 wherein the alternating switch is spring loaded and is activated by contact with the hammer member to supply current to the solenoid coil to move the hammer forwardly and away from the alternating switch, the spring acting to activate the alternating switch to supply current to the coil to move the hammer rearwardly and toward the switch when the switch is not being contacted by the hammer member.
 3. Assembly according to claim 2 further comprising a set of breaker points positioned adjacent the lever, said points being opened by the lever when the hammer member reaches its forwardmost position to cause electric current flow to the alternating switch, and a pushbutton switch to supply electric current to the coil to move the hammer rearwardly and close the breaker points.
 4. Assembly according to claim 1 further comprising a spring secured at one end to the casing and at the other end to the carriage and urging the carriage rearwardly, and a rack secured to the casing adjacent the nail driving rod and a spring-loaded lever carried by the rod engaging the rack to maintain the rod and carriage in a forward position during a nailing operation, said spring-loaded lever being disengaged from the rack when the rod and carriage reach their forwardmost position.
 5. Assembly according to claim 1 further comprising a forwardly projecting nail advancing rod carried by the carriage and parallel to the nail driving rod, said nail advancing rod advancing the nails in the nail supply magazine to maintain one nail in a position adjacent the nail passageway during the driving of a nail by the nail driving rod, and spring means urging the one nail into the nail passageway upon rearward movement of the carriage and the nail driving rod.
 6. Assembly according to claim 1 further comprising an air cylinder in association with the reversing switch, said air cylinder having adjustable ports therein to dampen the impact of the rearward movement of the hammer member.
 7. Assembly according to claim 1 further comprising parallel tracks secured within the casing and rollers mounted on the hammer member and carriage member engaging the tracks. 